The invention relates to a mechanical assembly for dosing and delivering a fluid.
Devices for dosing and delivering a fluid are widely used in consumer goods or in pharmaceutical industry. Such devices for dosing and delivering a fluid should allow a good control of the quantity of fluid dosed, as well as a good control of the delivery of this fluid dose. In particular in the pharmaceutical industry, accurate control of both the quantity and the delivery are critical. Furthermore, it is desired to produce such devices in a reproducible and economical manner. It is the object of this invention to provide accurate dosing and delivery of a fluid by means of an economical dosing and delivery device.
In accordance with the invention, this object is accomplished in a dispensing device for a fluid, the dispensing device comprising a reservoir, a shaft, a back seal, a damper, a piston and a one-way valve, the back seal sealing a first end of the reservoir and being displaceable along the shaft, the valve being on the second end of the reservoir, the piston being fixed to one end of the shaft, the piston being located between the valve and the damper, the damper being also fixed to the shaft, the damper being located between the piston and the back seal, whereby the piston has an opened position and a closed position, the open position allowing fluid communication between the valve and the part of the reservoir between the piston and the back seal, the displacement of the piston between the opened and the closed position being induced by a displacement of the shaft along its own axis, the pressure in the area comprised between the valve and the piston reducing when the piston is moved from its closed position towards its opened position, the damper collapsing when the piston is moved from its closed position towards its opened position, the only fluid flow from the part of the reservoir situated between the damper and the back seal and the part of the reservoir situated on the other side of the damper being a connecting passage situated in the damper when the piston is moved from its opened position towards its closed position.
A device formed in accordance to the invention has a number of advantages. Since the devices comprises a piston having an opened position and a closed position allowing fluid communication between the valve and the reservoir, the quantity of fluid to dispense can be accurately controlled by displacing the desired quantity of fluid from the reservoir to the valve part by displacement of the piston from the closed to the opened position, the absence of a direct link between the reservoir and the valve avoiding uncontrolled emptying of the reservoir through the valve. Further, as the pressure in the area comprised between the valve and the piston reduces when the piston is moved from its closed position towards its opened position, the displacement of the piston towards the opened position will necessitate the application of a force threshold sufficient to overcome or at least to balance the pressure reduction and internal system friction forces, so that undesired displacement of the piston is avoided. The delivery of the dose is also accurately controlled via the combination of the use of the one way valve, of the piston, of the damper and of the back seal. Indeed, the one way valve will allow delivery of the fluid only when the piston is displaced forward towards the valve, the speed of displacement of the piston being regulated by the size of the connecting passage provided in the damper combined with the fluid viscosity and applied mechanism force (e.g. spring force), thus allowing control on the speed of the fluid delivery through the valve.